This invention relates to a method and apparatus for buffing a tread to roughen its surface. The inner casing contacting surfaces of the tread are buffed such that the roughened surface provides a means for evacuation of entrapped air when mounted to a prepared tire casing.
In the mounting of replacement treads on a tire casing it is known in the art to buff the surface of the casing, removing the worn tread and roughening the remaining surface. This roughening of the casing improves the adhesion of a cushion layer of unvulcanized rubber is layered on and cemented to the cushion layer. This assembly is then cured.
It has been determined that a roughening of a casing contacting precured tread surface prior to cementing to the cushion layer improves the tread adhesion. The roughening procedure, commonly called buffing, is accomplished by the use of wire wheels. The wheels remove oxidized rubber and increase the surface area to be bonded, thus improving bonding characteristics. Conventional buffing of the casing and the precured tread were directed circumferentially creating minute grooves around the circumferential surface of the tread and the casing. These grooves provide areas where air can be entrapped. The grooves act as tiny seals and prevent air from being removed during assembly, and entrapped air weakens the bonding of the tread to the casing.
In the past, various means have been utilized to insure that entrapped air is evacuated from between the tread and the cushion layer. The placement of vent cords between the tread and the cushion layer is one example.
With regard to winged treads, trials have shown that circumferentially buffing at the inner curvature of the wing did not produce a uniform buff. Uniformity of buffing being important to bond quality required that an alternative method be developed.
It is the purpose of this invention to provide a method and apparatus for buffing a precured tread wherein the resulting roughened tread surfaces provides a means for improved air evacuation and an improved bond. This is accomplished by insuring that at least a portion of the roughened grooves terminate at the tread edges, thus providing a means for air evacuation.
It is a further purpose of this invention to describe and illustrate a method and apparatus for uniformly buffing a precured wing tread whereby the inner surfaces of the wings are uniformly roughened such that the grooves extend to a tread edge.